Electrical switching and memory phenomena in organic multilayer films

We have observed electrical switching and memory phenomena in multilayer films of arylamines prepared by vapor deposition through a shadow mask to produce devices with an active area of ~ 1 mm2. Each device is a sandwich structure with a hard to oxidize hole transport compound (TPD) on the Ag electrodes and a redox-gradient dendrimer (4AAPD) in between. Representative current-voltage curves are shown below and indicate that the device can be switched from a high resistance state to a conductive state when the external applied voltage exceeds a threshold of ~ -0.4 V. At about –0.2 V the current in the conducting state is three orders of magnitude larger than the unswitched state, which allows for easy discrimination between the “written and unwritten bit”. After switching, the resistance of the device drops slightly from ~ 1000 to 500 ohms after two days of storage under ambient conditions. Similar results have measured in thinner multilayer films. These results demonstrate the ability to write and read data states in molecular media. At present these are write once memory devices and we are trying strategies to erase.